Various mobile or portable electronic devices may have reduced power consumption by operating some of the systems within these devices at low voltages (e.g., 3.0 volts, 1.5 volts, etc.). A power management unit within such devices can convert an input voltage to several supply domains with different output voltages and requirements. For example a digital block might need voltage scaling capability, whereas analog parts may each need a different supply voltage. Such devices or systems can easily end up with many different supply domains.
The power conversion between input and output voltage is often done with low-dropout regulators (LDOs). LDOs can generally operate efficiently at low voltages and can provide a regulated output using small differential input-output voltages. A regulated output from a LDO is commonly based on a comparison of a feedback signal from the output of the regulator to a reference voltage.
However, output voltage overshoot can occur on start-up of a LDO. Overshoot is defined as the peak voltage above a nominal voltage for any step input at the LDO. Higher overshoot voltages can compromise the reliability of a circuit coupled to the output of a LDO, if not cause destruction of the circuit. For example, voltage overshoot can commonly be at least 100 mV over nominal on LDO start-up.